A known navigation apparatus learns a new road unregistered in a ready-made map data based on a travel trace of a movable body such as a vehicle and the like. For example, a road learning function learns a new road (a learned road) unregistered in the map data, by generating and storing the new road based on a travel trace from a point where the present position of the movable body departs from a prestored road in the map data to a point where the present position of the movable body returns to the prestored road in the map data.
As for an in-vehicle navigation apparatus, a route guidance method for circular intersection is known (see JP-2007-71601A1 corresponding to US 2007/0055444A1). The circular intersection is, for example, a traffic, circle, a roundabout, a rotary etc. A conventional circular intersection guidance is, for example, so called an exit-number-type circular intersection guidance, which tells how many exits there are with respect to the entrance of the circular intersection. For example, a message indicating that please exit from the second exit ahead may be provided.
In JP-2005-156278A1, a circular intersection is transformed to an intersection in which a circular road is a straight road and multiple connection roads are connected to this straight road. Then the transformed intersection is displayed, and additionally, an exit number is used to indicate where an exiting road is located with respect to an entrance road.
The inventors of this application have found out the following. Since the above conventional circular intersection guidance leaves a guidance about a learned road out of consideration, various problems may emerge when the conventional circular intersection guidance is applied to a circular intersection to which both of the road (prestored road) prestored in the map data and the learned road obtained by the road learning function are connected.
For example, let us assume that both of the prestored road and the learned road are present as exits (exiting roads) of a circular intersection. In this case, the circular intersection guidance using the exit number may assign a series of exit numbers to the exiting roads (the prestored road and learned road), and may provide the guidance about an exiting road of the circular intersection based on the exit numbers. In the above situation, because the exit number of the learned road is added, the exit numbers of the prestored roads may be changed or the exit numbers may not arranged in ascending order in the heading direction of the vehicle. Thus, a user may have a difficulty in grasping the guidance about the exiting road. Moreover, if a navigation apparatus updates the exit numbers of the circular intersection in accordance with its own rule, the updated exit number may not coincide with actual exit numbers.